Oral pain relievers are typically prescribed for treatment of acute and chronic pain, including arthritic pain, musculoskeletal pain, and neuropathic pain. Oral pain relievers often have side effects, some of which can be severe. Topical pain relievers work locally and are less likely to cause severe systemic side effects. Some topical pain relievers include non-steroidal anti-inflammatory drugs (NSAIDs), salicylates, lidocaine, capsaicin, amitriptyline, glyceryl trinitrate, opioids, menthol, and gabapentin.
Research suggests that NSAIDs are most effective as topical pain relievers for a number of conditions including joint-related conditions; however, they may not be suitable for all subjects experiencing pain, due to allergies, drug intolerances or contraindications such as renal failure, hypertension or gastric ulcers from absorption of topical NSAIDs.
Some other topical pain relievers are classified as counterirritants, such as menthol, capsaicin and camphor, which work by creating a burning or cooling sensation that distracts the person from the actual pain. Capsaicin in particular causes undesirable side effects including burning and stinging.
There is a need for alternative topical pain relievers with minimal side effects, and without unpleasant localized cooling and burning sensations.
Mannitol is a sugar alcohol with the formula C6H8(OH)6. It reduces intracellular water retention and also has free radical scavenging properties. Mannitol's most common uses are related to its function as an osmotic diuretic, thereby making it a suitable agent for treating kidney failure, reducing swelling in the brain and eye, and treating cystic fibrosis. Mannitol is also used as a sweetener in chewing gum and for diabetics.
Mannitol has been shown to be effective in pain management when injected under the skin or intravenously. For example, intravenous mannitol reduces neuro-inflammation by reducing edema. In addition, injection of mannitol just under the skin is used to treat neuropathic pain. Finally, dental anaesthesia is more effective when mannitol is included with the standard nerve block agents, lidocaine and epinephrine.
Mannitol has been used for treating pain intravenously and subcutaneously, but never topically.